Obesity link to brain structure in explosive medical study

Researchers said the findings could explain why overweight people make poor diet choices

Overweight people are less intelligent than people who are do not have weight problems , a provocative study claims.

Overweight men and women have less grey and white matter in key areas of the brain, it suggests. They also have greater impulsiveness and “altered reward processing”, the study said.

The researchers said that their findings could explain why overweight people make poor diet choices – they do not have the mental capacity to control themselves.

The theory is likely to prove controversial as weight loss campaigners have emphasised that the issues behind weight problems vary from individual to individual.

The research involved sophisticated brain images of 32 adults – 16 men and 16 women – selected from the US city of Baltimore, in Maryland.

Anyone who had a history of brain damage, substance abuse or mental illness was excluded from the group.

Outlining the object of the study, the authors said: “It has been suggested that body composition itself might somehow affect the neural systems that underlie cognition, motivation, self-control and salience processing, which would in turn affect one’s ability to make better lifestyle choices, forgoing immediate and/or highly salient rewards for the sake of longer-term health and wellness goals.”

The researchers measured Body Mass Index, a commonly-used measure of how overweight a person is, and body fat percentages and compared them to differences in brain structure and function.

Lead researcher Chase Figley, an assistant professor in the department of radiology at the University of Manitoba, said that the brain scans were “very thorough”.

He said they covered changes across the whole brain, but also “specific networks”.

In particular he was interested in the “salience network”, which he described as the “seat of motivation, willpower, and the ability to persevere through physical and emotional challenges”.

The results showed that there was “no significant difference” in terms of white matter between people who had a normal weight and people who were overweight.

These changes could further affect the ability of overweight individuals to exert self-control and maintain healthy lifestyle choicesProf Chase Figley

In a surprise twist, people with a higher BMI actually had slightly more grey matter overall.

However, looking at specific networks on the brain a different picture began to emerge. In particular, heavier and fatter people had less white matter in the salience network.

There were also differences in the dorsal striatum, an area of the brain involved with habitual behaviour.

Professor Figley told the National Post, a Canadian newspaper: “It stands to reason that these changes could further affect the ability of overweight individuals to exert self-control and maintain healthy lifestyle choices.”

He added that it was not clear if the brain differences predispose certain individuals to becoming fat, or vice versa.

However, he said: “There are previous studies that imply elevated body fat can cause these sorts of brain changes.”

Prime Minister David Cameron says he needs to lose weight

Two-thirds of men and 57 per of women in Britain are categorised as being overweight or obese, the highest such rates in Europe. Some 26 per cent of boys and 29 per cent of girls are overweight or obese, compared to 17.5 per cent and 21 per cent in 1980.

The study was reported in the journal Frontiers in Neuroscience.

What kind of fat are you?

SKINNY FAT

Characterised by:

Poor diet and exercise regime

Healthy or low BMI

Lack of muscle tone

Poor metabolic health (high-blood lipids, high blood glucose, visceral fat). Visceral fat is normally present when there is a large build-up of fat around the abdominal area.

In more extreme cases, visceral fat can coat the internal organs, leading to serious cardiovascular health problems and diabetes.

How to tackle it:

Identify problem areas by measuring body fat using callipers; a DEXA scan can reveal the presence of visceral fat.

Building muscle is key: an exercise programme should stress cardiovascular and muscle resistance.

Diet should then support the exercise demands: make sure you are fuelled properly if you’re exercising (carb intake should match exercise demands).

Eat little and often to control blood sugar fluctuations and eliminate refined carbohydrates, sugar and alcohol.

Sip herbal tea instead of caffeine (a stimulant makes you more stressed, causing more release of cortisol, thus more fat around the middle).

Food also plays an important role in stress relief. Making healthy food choices – balanced protein, fresh fruit such as raspberries, blueberries and cherries, and vegetables – will aid a sense of wellbeing. Avocado, asparagus and nuts are good healthy, stress-relieving foods to include.